The Physiology Core was established as a new Core at the last competing renewal in 2002 and consolidates the expertise and experience related to in vivo measures of parameters of glucose tolerance and physiological regulation of carbohydrate metabolism accumulated over more than 25 years by DRTC investigators. This Core provides assistance to DRTC investigators with the use a wide array of clinical research procedures for assessing insulin secretion, insulin sensitivity, and factors regulating glucose tolerance. It provides consultative, technical, analytical and interpretative support. The Physiology Core also offers services related to sleep assessment. The Core maintains an IRB-approved series of protocols for human studies covering a wide range of procedures including studies of glucose regulation and energy balance in the General Clinical Research Center, ambulatory evaluation of glucose regulation and assessment of sleep-wake regulation and sleep disordered breathing. The Physiology Core thus ensures that investigators involved in clinical diabetes research have access to a wide range of well-validated, standardized methods for in vivo evaluation of parameters of glucose tolerance. The Core provides assistance with a large variety of analytical methods, including, among others, use of the minimal model for estimation of insulin sensitivity, use of deconvolution for estimation of insulin secretion rates, analyses of hormonal pulsatility, and interpretation of sleep studies. Dr. Eve Van Cauter will serve as Director and Dr. Plamen Penev as Co-Director.